Compressor unloading mechanism



Jan. 15, 1963 R. J. HACKBART ETAL 3,073,510 I COMPRESSOR UNLOADIINGMECHANISM Filed Dec. 29, 1960 2 Sheets-Sheet 1 I8 I Q g E Q mm 55335?ROA CH ATTORNEYS Jan. 15, 1963 R. J. HACKBART EI'AL COMPRESSOR UNLOADINGMECHANISM 2 Sheets-Sheet 2 Filed Dec. 29, 1960 INVENTOR. REUBEN J. HACKBART E C. R CA CH Ill! A T T OR N E Y S United States Patent 3,073,510COMPRESSOR UNLOADING MECHANISM Reuben J. Hackbart and Jerome C. Roach,La Crosse, Wis., assignors to The Trane Company, a corporation ofWisconsin Filed Dec. 29, 1960, Ser. No. 79,318 6 Claims. (Cl. 230--30)This invention relates generally to reciprocating compressors and morespecifically to refrigeration reciprocating compressors with unloadingmeans to vary the output capacity of the compressor.

-An object of the invention is to provide a reciprocating compressorwith a unique unloading mechanism which allows the output of thecompressor to be varied while substantially maintaining constant speed.

A second object of the invention is to provide a reciprocatingcompressor which incorporates an unloading mechanism that is inexpensiveto manufacture and easy to assemble and repair. A further object of theinvention is to provide a reciprocating compressor with a two pieceunloading mechanism which allows the capacity of the compressor to bevaried without excessive .wear on the unloading mechanism.

A fourth object of the invention is to provide a reciprocatingcompressor which employs a two piece unloading mechanism actuated by oilpressure from the compressor oil pump in response to the suctionpressure of the refrigeration system.

A still further object of the invention is to provide a reciprocatingcompressor which employs an oil pressure actuated two piece unloadermechanism in which the control oil is fed to the unloader mechanismthrough the wall between the crankcase and the section chamber.

Other objects and advantages of the invention will be clearly apparentas the specification proceeds to describe the invention with referenceto the accompanying drawings in which:

, FIGURE 1 is a partial sectional view showing our new and novelunloading mechanism;

FIGURE 2 is a sectional view of a cylinder and unloading mechanismshowing a modification of that shown in FIGURE 1;

FIGURE 3 is another sectional View of a cylinder and unloading mechanismshowing a still further modification of the unloading mechanism shown inFIGURE 1; and

FIGURE 4 is a partial bottom view of the unloading piston of FIGURE 3.

Referring now to FIGURE 1, numeral 10 designates a multi-cylinderrefrigeration compressor in which is shown our new and novel unloadingmechanism. For the purpose of description only one cylinder is shown butit is obvious that our novel mechanism can be applied to as manycylinders of the compressor 10 as desired. Our new and novel unloadermechanism is an improvement over that shown in Labus, Patent No.2,673,025, March 23, 1954 and is controlled in the manner shown in thispatent.

In normal operation, suction gas is drawn into the common suctionchamber 12 from the evaporator 14 through suction line 15 on the suctionor downstroke of'piston 16. Piston i6 is driven through a connecting rod18 by a crankshaft, not shown. As the piston de scends further thesuction gas from the suction chamber 12 is drawn through suctionpassages 20 and spring biased suction valve 22 into the cylinder definedby cylinder liner 24.

On the compression or upstroke of the piston 16 compressed refrigerantis discharged past spring biased dis- 3,973,510 Patented Jan. 15, 1953charge valve 26 into the common discharge chamber 28. This compressedrefrigerant is then delivered to condenser 30 by conduit 32 wherein itis condensed and delivered to evaporator 14 through receiver 33 andexpansion means 34. This cycle is well known in the art and notconsidered part of the invention.

Looking now specifically at the unloading mechanism, numeral 36represents the unloading piston which reciprocates in annular wallmember 38 which is integral with partition 40 separating the crankcase42 from the suction chamber 12. 'Abutting shoulder 41 on cylinder liner24 and engaging piston 36 is an annular ring member 44 which also abutsthe head 46 of pins 48 slidably mounted in holes 50. The holes 50 arealternated with the suction passages around the periphery of the upperportion 52 of the cylinder liner 24. Springs 54 act against heads 46 ofpins 48 to urge the pins downwardly away from suction valve 22.

An annular ring member 58 abuts shoulder 56 on wall member 38 to retainthe annular O-ring seal members 60 and 62 within the seal retainer 64. Asnap ring is snapped into recess 66 to retain the annular seal retainer64, O-rings 60 and 62, and ring member 58 in assembled relationship. Itis abvious that O-rings 60 and 62 prevent oil from leaking into thesuction chamber and thereby being carried into the refrigeration system.

It should be noted that unloading piston member 36 basically consists ofan annular leg portion 67 which has a surface 68 which slidably engagescylinder 24, a seat or base portion 70 perpendicular to annular surface68 to form a retaining surface for spring '72, and another annular legportion 73 which has a surface '74 slidably engaging wall 38 and beingsubstantially parallel to annular surface 68 and perpendicular to seatportion 70. It should be noted that a gap could be left between thecylinder liner 24 and the annular piston member 36 to provide a heatbarrier, if desired.

Spring member 72 is a single annular spring located between wall 40 andthe unloading piston 36 to bias the unloading piston 36 upwardly.

Operation In operation, as described in aforementioned Labus Patent No.2,673,025, the compressor will start unloaded as shown or will unloadduring operation of the compressor responsive to suction pressure. Ifdesired, the unloader control mechanism, not shown, may be controlled byother means such as discharge pressure, if desired.

Assuming the cylinder is unloaded as shown, the operation will be hereindescribed. As shown, suction valve 22 is held open by pin members 43 dueto the action of spring 72 on the unloading piston 36. Unloading piston36 in turn acts on pin head 46 through ring mem ber 44 to overcome thebias of springs 54 to force the suction valve 22 to the open position asshown.

Assuming now that the capacity of the cylinder is re quired to handlethe load, oil will be fed through oil line 76, oil connection 77, oilpassage 78 to cavity St? between the ring member 58 and the pistonmember 36. This oil 4 leakage of oil from the cavity 30 when oil isbeing provided to the cavity.

If the controlling means, not shown, senses a change in condition suchthat the operation of the cylinder is unnecessary the oil pressure willbe cut off and oil in cavity 80 will bleed back out of the oil passage78 and oil line 76. At the same time oil will also leak past unloaderpiston 36 into spring cavity 82 and bleed through aperture 84 into thecrankcase 42. Aperture 84 not only serves to readily bleed the cavity 80when the oil pressure is cut off but also serves to allow any oil thatleaks into spring cavity 82 when oil pressure is being supplied tocavity 80 to be returned to the crankcase 42. When the oil pressure hasbeen relieved from cavity 80 spring 72 will act on piston 36 in themanner previously described.

FIGURES 2-4 are modifications of the unloader mechanism shown inFIGURE 1. In all the figures of this application like parts will beshown and described with the same reference number.

FIGURE 2 is basically the same as FIGURE 1 except the unloading pistonhas been modified. The unloading piston 92 of FIGURE 2 is L-shaped andhas a leg portion 93 slidably engaging the cylinder liner 24 and a baseportion 95 which abuts shoulder 86 of annular wall 38 instead ofabutting the wall 40 as in FIGURE 1 to provide a limit for downwardmovement of the piston member and to prevent leakage of oil into thespring pocket 82 and bleed hole 84 when oil is being supplied to cavity80. The operation of the modification of FIGURE 2 is the same as that ofFIGURE 2. The modification of FIG- URE 2 provides an unloading pistonwhich is more readily machined and assembled into position.

The modification of FIGURES 3 and 4 is also basically similar to thatshown in FIGURE 1. In FIGURE 3 an annular unloading piston 94 consistingof annular leg portion 97, base portion 99, and leg portions 96 and 98is employed and individual springs 88 are used in the spring pockets 90instead of an annular spring member such as that used in the first twodesigns. The annular leg portion 96 of the unloading piston 94 is longerthan the leg portion 98 of the unloading piston 94 in order to seal thespring pockets 90 and the bleed hole 84 from the cavity 80 when oil isbeing supplied to cavity 80. The operation of this unloading is also thesame as the preferred embodiment shown in FIGURE 1.

The herein disclosed new and novel unloader mechanism provides manyadvantages not present in the prior art. Our two piece unloaderobviously is more readily assembled and cheaper in cost since the numberof elements present are considerably less than that presently in use.Further, our two-piece unloader provides a construction which greatlylessens the possibility of damage to the O-ring seals since ourconstruction has only one O-ring exposed to a moving surface, which ofcourse is the unloading piston. In contemporary compressors breakage ofthe seal members causes a great deal of unnecessary expenditure of timeand money in order to replace such elements. Our design furtherincorporates a bleed hole to increase the response of the unloadingmechanism to the changes in the controlling condition. Obviously ourbleed hole design allows the compressor to unload faster than one whichdoes not provide a secondary means to feed the oil back to thecrankcase.

Although we have described in detail the preferred embodiment of ourinvention, we contemplate that many changes may be made withoutdeparting from the scope or spirit of our invention, and we desire to belimited only by the claims.

We claim:

1. In a compressor having a compressing cylinder, said cylinder beingdefined by a cylinder liner, a suction chamber, a discharge chamber, acrankcase, a crankcase wall member separating said crankcase from saidsuction chamber, said wall member having an annular upstanding portiondefining an annular chamber between said upstanding portion and saidcylinder liner, said compressing cylinder having associated therewith asuction valve through which gaseous medium may be admitted from saidsuction chamber and a discharge valve through which compressed gaseousmedium may be discharged into said discharge chamber, and fluid pressureresponsive means to control the unloading of said cylinder, said fluidpressure responsive means comprising: an annular piston member slidablymounted in said annular chamber and surrounding said cylinder liner,valve engaging means supported on said annular piston member, springmeans acting against said annular piston and tending to move saidannular piston member and said valve engaging means toward said suctionvalve to force said suction valve to open position, sealing meansoperably associated with said annular piston member and forming a cavitytherebetween, means forming a passage in said annular wall member, saidpassage communicating with a source of fluid to supply fluid to saidcavity in response to the load imposed on said compressor in order toforce said annular piston member downwardly against the bias of saidspring means to allow said suction valve to close, and means forming ableed hole in said crankcase well member and communicating with saidannular chamber to decrease the response time of said fluid pressureresponsive means.

2. In a compressor having a compressing cylinder, said cylinder beingdefined by a cylinder liner, a suction chamber, a discharge chamber, acrankcase, a crankcase wall member separating said crankcase from saidsuction chamber, said wall member having an annular upstanding portiondefining an annular chamber between said upstanding portion and saidcylinder liner, said compressing cylinder having associated therewith asuction valve through which gaseous medium may be admitted from saidsuction chamber and a discharge valve through which compressed gaseousmedium may be discharged into said discharge chamber, and fluid pressureresponsive means to control the unloading of said cylinder, said fluidpressure responsive means comprising: an annular piston member slidablymounted adjacent said cylinder liner and in said annular chamber, saidannular piston member having an L-shaped section composed of a legportion and a base portion, said leg portion slidably engaging saidcylinder liner, said base portion slidably engaging said upstandingannular wall portion and dividing said annular chamber into a firstannular chamber and a second annular chamber, valve engaging meansseparate from and supported on said annular piston, spring means actingagainst said annular piston and tending to move said annular piston andsaid valve engaging means toward said suction valve to force saidsuction valve to open position, sealing means supported in said firstannular chamber and forming a cavity between said sealing means and saidbase portion of said annular piston, means forming a passage in saidannular wall member, said passage communicating with a source of fluidto supply fluid to said cavity in response to the load imposed on saidcompressor in order to force said annular piston member downwardlyagainst the bias of said spring means to allow said suction valve toclose and means forming a bleed hole in said crankcase wall member andcomma-- nicating with said second annular chamber to readily returnfluid from said cavity to said crankcase.

3. The structure of claim 2 wherein an annular shoulder is provided insaid annular upstanding portion to limit the downward movement of saidannular piston member and to form a fluid seal.

4. In a compressor having a compressing cylinder, said cylinder beingdefined by a cylinder liner, a suction chamber, a discharge chamber, acrankcase, a crankcase wall member separating said crankcase from saidsuction chamber, said wall member having an annular upstanding portiondefining an annular chamber between said upstanding portion and saidcylinder liner, said compressing cylinder having associated therewith asuction valve 3 tion valve to force said suction valve to open position,I 1 50,230 Australia Dec. 13, 1254 7 8,073,510 s I e through whichgaseous medium may be admitted from sealing means supported in saidfirst annular chamber said suction chamber and a discharge valve throughand forming a cavity between said sealing means and WhlCh compressedgaseous medium may be discharged said base portion of said annularpiston, means forming a into said discharge chamber, and fluid pressureresponpassage in said annular wall member and communicating sive meansto control the unloading of said cylinder, said with a source of fluidto supply fluid to said cavity in refluid pressure responslve meanscomprising: an annular spouse to the load imposed on said compressor inorder piston member slidably mounted adjacent said cylinder to forcesaid annular piston member downwardly against liner and in said annularchamber, said annular piston the bias of said spring means to allow saidsuction valve member having an L-shaped section composed of a leg toclose, and a bleed hole in said crankcase wall member portion and a baseportion, said leg portion slidably en- 10 communicating with said secondannular chamber to gaging said cylinder liner, said base portionslidably readily return fluid from said cavity.

engaging said upstanding annular wall portion and divid- 6. In acompressor having a compressing cylinder, said ing said annular chamberinto a' first annular chamber cylinder being defined by a-cylinderliner, a suction chant:

. and a second annular chamber, said annular piston memher, a dischargechamber, a crankcase, a crankcase wall her having a second leg portionlying substantiallyparallel member separating said crankcase from saidsuction chame V to the leg portion of said L-shaped section and slidablyher, said wall member having an annular upstanding porengaging saidannular upstanding wall portion, said section defining an annularchamber'between said upstandond leg portion abutting said crankcase wallmember ing portion and said cylinder liner, said compressing cylin--when said annular piston member is in the down posider having associatedtherewith a suction valve through tion to provide a downward'limit forsaid annular piston which gaseous medium may be admitted from saidsucmember, valve engaging means supported on said annular tion chamberand a discharge valve through which coma P pr g means g against saidannular piston pressed gaseous medium may be discharged into said disandtending to move said annular piston and said valve charge chamber, andfluid pressure responsive means to engaging means toward said suctionvalve to force said control the unloading of said cylinder, said fluidpressure suction valve to open position, sealing means supportedresponsive-means comprising: an annular piston member in said firstannular c amb r and forming a v y slidably mounted adjacent saidcylinder liner and in said between said sealing means and said baseportion of said annular chamber, said annular piston member havingannular piston, and means forming a passage in aid an L-shaped sectioncomposed of a leg portion and a base ann lar wall m m er and comm nicaing wi h a ourc portion, said leg portion slidably engaging saidcylinder of fluid t0 PP Y fluid to said cavity in t ponseto the liner,said base portion slidably engaging saidupstanding load imposed 011 saidCompressor in Order force Said 7 annular wallportion and dividing saidannular chamber annular Piston member nw y against the bias into a firstannular chamber and a second annular chamof said spring means to allowsaid suction valve to close. her, said annular piston member having asecond leg por- In a compressor having compressing cylinder, d t-ionlying substantially parallel to the leg portion of said cylinder beingdefined y a 1 cylinder a suction L-shaped section and slidably engagingsaid annular up- Qhamber, a discharge fi fl a se, crankcase I standingwall portion, said second leg portion abutting said wall-memberseparating said crankcase from said succrankcase wall member when saidannular'piston member 11011 chambfil, said Wall member having an r P- isin the down position to provide a downward limit for standing Portiondefining an annular chamber htZ said annular piston member, valveengaging means sup- Said upstamling Portion said cylinder n r, Said 40ported on said annular piston, spring means acting against compressingcylinder having associated therewith a 8 said annular piston and tendingtomove said annular piston tion valve through hich gaseous medium may bea and said valve engaging means toward said suction valve mitted fromsaid suction chamber and a discharge valve I to force said suction valveto open position, sealing means through-which compressed gaseous mediumay be dis; supported in said first annular chamber and forming a chargedIQ said discharge'chambeli n fluid p e '45 cavity between said sealingmeans and said base portion responsive means'toicontl'ol'rthe, unloading01 a d cylim ofsaid annular piston, means forming a passage in said,der, Said fluid P sponsive means compri ing: I V annular wall memberand communicating with a source of an annular Piston membef$1id8b1Ymounted adjacent Said fluid to supply fluid to said cavity in responseto the load cylinder liner and in Said annular chamber, Said an iimposed on said compressorin order to force said annular 1 I Pistonmember'haviflg an h p Section composed of a piston member downwardlyagainst the bias of said spring leg portion and a base portion, said legportion-slidably means to allow said suction valve to close and a bleedf engaging Said cylinder l Said base P 5 i 8 Y hole in said crankcasewallmember communicating s s s said upstanding annular wall p tanddivid-ins with said second annular chamber to readily return fluid 1said annular chamber into a first annular chamber and from saidicavity.I r a second annular chamber, said annular piston member a havingasecond leg portion lying substantially parallel H ReferencesCitedin thefile of this patent t th leg pardon (if said tL-slhapedasiecltliglligndszligizlglcy UNITED/STATES PATENTS engaging sai annuarups an mg w r n, v

v 2,555,005 .Warneke May- 9, 1951 ond leg portion abutting saidcrankcase wall mem I Labus'et a1; ,uruu Mar. 23, 1954 when saidannular pston member is m-the down pos1- 9 2,956,729 c s y: l y octl 0 tion toprovide a downward limit for said annular piston i .r member, valveengaging means separate from and sup- 2,971,690 Nlcholas F 1961 portedon said annular piston, spring means acting against said annular pistonand tending to move said annular. -piston and said valve .engaging meanstoward said suc-

1. IN A COMPRESSOR HAVING A COMPRESSING CYLINDER, SAID CYLINDER BEINGDEFINED BY A CYLINDER LINER, A SUCTION CHAMBER, A DISCHARGE CHAMBER, ACRANKCASE, A CRANKCASE WALL MEMBER SEPARATING SAID CRANKCASE FROM SAIDSUCTION CHAMBER, SAID WALL MEMBER HAVING AN ANNULAR UPSTANDING PORTIONDEFINING AN ANNULAR CHAMBER BETWEEN SAID UPSTANDING PORTION AND SAIDCYLINDER LINER, SAID COMPRESSING CYLINDER HAVING ASSOCIATED THEREWITH ASUCTION VALVE THROUGH WHICH GASEOUS MEDIUM MAY BE ADMITTED FROM SAIDSUCTION CHAMBER AND A DISCHARGE VALVE THROUGH WHICH COMPRESSED GASEOUSMEDIUM MAY BE DISCHARGED INTO SAID DISCHARGE CHAMBER, AND FLUID PRESSURERESPONSIVE MEANS TO CONTROL THE UNLOADING OF SAID CYLINDER, SAID FLUIDPRESSURE RESPONSIVE MEANS COMPRISING: AN ANNULAR PISTON MEMBER SLIDABLYMOUNTED IN SAID ANNULAR CHAMBER AND SURROUNDING SAID CYLINDER LINER,VALVE ENGAGING MEANS SUPPORTED ON SAID ANNULAR PISTON MEMBER, SPRINGMEANS ACTING AGAINST SAID ANNULAR PISTON AND TENDING TO MOVE SAIDANNULAR PISTON MEMBER AND SAID VALVE ENGAGING MEANS TOWARD SAID SUCTIONVALVE TO FORCE SAID SUCTION VALVE TO OPEN POSITION, SEALING MEANSOPERABLY ASSOCIATED WITH SAID ANNULAR PISTON MEMBER AND FORMING A CAVITYTHEREBETWEEN, MEANS FORMING A PASSAGE IN SAID ANNULAR WALL MEMBER, SAIDPASSAGE COMMUNICATING WITH A SOURCE OF FLUID TO SUPPLY FLUID TO SAIDCAVITY IN RESPONSE TO THE LOAD IMPOSED ON SAID COMPRESSOR IN ORDER TOFORCE SAID ANNULAR PISTON MEMBER DOWNWARDLY AGAINST THE BIAS OF SAIDSPRING MEANS TO ALLOW SAID SUCTION VALVE TO CLOSE, AND MEANS FORMING ABLEED HOLE IN SAID CRANKCASE WELL MEMBER AND COMMUNICATING WITH SAIDANNULAR CHAMBER TO DECREASE THE RESPONSE TIME OF SAID FLUID PRESSURERESPONSIVE MEANS.